1. Field of the Invention
The present invention relates to biological aerosol detection. In particular, the present invention relates to a triggering device for warning of biological aerosol contaminants. Most particularly, the present invention triggers a suite of biological sample collectors with the positive indication of the presence of an aerosol biological contaminant.
2. Brief Description of the Related Art
With the threat of biological aerosol contaminants to military units and civilian communities, several systems have been developed to provide standoff detection of the biological agents. Although some of the systems possess substantial range capabilities, such as up to 100 kilometers, to detect generated biological aerosols, the systems are generally large and consume considerable power. In many circumstances, use of the large systems becomes problematic, such as being used in conjunction with a small mobile force, or in isolated areas. In these situations, smaller point sensors are needed.
Generally, smaller point sensors provide a reduced capability in detecting aerosol agents. One method of increasing the capability of the sensor was to develop an instrument that provided a trigger for a suite biological sample collectors. The triggering method was based on an increase in the concentration of a particular sized particle, however, the method proved in-effective for field operations.
One technology used to determine the presence or absence of biological contaminants includes an instrument called Laser Induced Fluorescence. All biologically based materials are composed of proteinaceous molecules, which auto-fluoresce when exposed to electromagnetic radiation, i.e. light, at an excitation wavelength. The excitation wavelength is any wavelength that couples into the absorption band of the biological compound sample. Once the compound adsorbs the radiation, the radiation is elastically (directly scattered) and inelastically (fluorescence) scattered. The inelastic scatter signature indicates whether the compound is biological in nature.
Previous three point sensors, based on laser induced fluorescence of biological materials, have experienced problems. In one design developed by Lincoln Labs of Concord, Mass., laser beams interact with the biological aerosol in a volume that is imaged onto two detectors with two large concave mirrors. Although the design appears to work well, it is very sensitive to misalignment and internal component contamination. Another design developed by Science and Technology Corporation of Hampton, Va. in conjunction with the Laser Standoff Detection Team of Chemical Biological Center, Aberdeen Proving Ground, Md. takes advantage of natural wind flow through the instrument and does not use mechanical pumps. As an open optical system, this design possesses the disadvantage of allowing solar radiation to enter the system, increasing system noise. Optical baffling may decrease the signal noise, but baffles also disrupt airflow through the system. Other point type triggers have not eliminated the problems of laser beam misalignment and instrument contamination.
Integrating spheres are optical instruments used primarily for optical calibration of detectors and sources. Integrating sphere are described in xe2x80x9cA Guide to Integrating Sphere Theory and Applicationsxe2x80x9d published by labsphere(copyright) of North Sutton, N.H., the disclosure of which is herein incorporated by reference.
In view of the foregoing, it is therefore an object of the present invention to eliminate the need to maintain alignment of the laser beam within the aerosol sample volume in relation to the point sensor detector elements.
These and other objects are achieved by the present invention which includes an aerosol triggering device, comprising a conduit forming a passage for an air flow, said conduit including an aerosol intake port and an aerosol exit port, wherein an air flow is capable of passing into said conduit through said aerosol intake port and exiting said conduit through said aerosol exit port; an optical chamber having at least two detectors capable of detecting an increase in the presence of a biological aerosol within an air flow, said optical chamber being in gaseous and optical communication with said conduit, wherein air flow entering said aerosol intake port is capable of entering said optical chamber prior to exiting through said aerosol exit port; a laser beam entrance window attached to said conduit and permitting entry of a laser beam into said conduit and said optical chamber; a laser beam exit window attached to said conduit capable of optical alignment with said laser beam entrance window; and, a laser beam system having a laser beam generation source capable of optically directing a laser beam of a selected frequency into said conduit and said optical chamber, wherein biological aerosol contaminants within an air flow emit elastic and inelastic scattering. The optical chamber comprises an integrating sphere.
The present invention further includes a method for detecting biological aerosols comprising the steps of providing an aerosol triggering device, comprising a conduit forming a passage for an air flow, said conduit including an aerosol intake port and an aerosol exit port, wherein an air flow is capable of passing into said conduit through said aerosol intake port and exiting said conduit through said aerosol exit port, an optical chamber having at least two detectors capable of detecting an increase in the presence of an aerosol within an air flow, said optical chamber being in gaseous and optical communication with said conduit, wherein air flow entering said aerosol intake port is capable of entering said optical chamber prior to exiting through said aerosol exit port, a laser beam entrance window attached to said conduit and permitting entry of a laser beam into said conduit and said optical chamber, a laser beam exit window attached to said conduit capable of optical alignment with said laser beam entrance window, and, a laser beam system having a laser beam generation source capable of optically directing a laser beam of a selected frequency into said conduit and said optical chamber, wherein biological aerosol contaminants within an air flow emit elastic and inelastic scattering; opening the aerosol intake port, wherein an air flow enters the conduit and into the optical chamber; energizing the laser beam system, wherein the laser beam generation source directs a laser beam into the optical chamber, causing an interaction between the laser beam and air flow; and, detecting the resulting interaction between the laser beam and air flow, wherein the presence of biological contaminants is determined.
Other and further advantages of the present invention are set forth in the description and appended claims.